1. Field of the Invention
The invention is a work-holding apparatus adapted to hold stock in a preselected relation to a cutting member in a table power tool, and more particularly, to holding the stock so as to permit movement along a single axis, particularly suited to holding wood on a table saw, shaper or router having a rip fence.
2. Description of the Related Art
A shortcoming in the prior art work holding apparatus remedied by the invention is the prior art's inability to hold stock vertically fixed against both upward and downward movement while permitting a smooth, sliding feed longitudinally. The second shortcoming addressed by the invention is the difficulty the prior art has in maintaining a normal angle to a table when long stock is held vertically for cutting the end of the stock. These problems and the invention's solutions can be seen in reviewing the prior art and the description herein.
Table power tools, and particularly table saws, use the table to provide a smooth surface on which stock can be moved into the blade with improved precision over hand-held saws. A rip fence comprising a rail extending longitudinally parallel to the blade is used to limit horizontal movement of the stock in one direction. Angled cuts are made using a calibrated miter gauge typically slidably carried in a slot recessed in the table. The miter gauge and rip fence are generally mutually exclusive. Router tables and shaper tables use similar attachments.
The aforementioned prior art is generally satisfactory for non-precision work, particularly where a single cut is made through a board lying flat on the table and held manually. Increased utility can be provided through various jigs, or other support or work-holding members. Various methods have been tried in the prior art to limit movement to a desired axial component along a single, substantially longitudinal axis. Owing to factors such as the imprecision in dimensioned lumber, forces induced by the cutting blade, "chatter" induced by blade geometry and other factors, and difficulties in holding stock held vertically, the prior art provides inadequate control.
Prior art attempts to solve certain of these problems include the carriage jig shown representatively in Cowley, U.S. Pat. No. 2,895,513 issued Jul. 21, 1959. This is a right angle fixture which fits in the slot for the miter gauge and includes a single clamp. Cowley neither is capable of holding large, vertically extending stock, nor does it have any inherent control against vertical movement generally, or angular movement around a horizontal axis, except for the weight of the assembly and the downward pressure of the operator who is also pushing the work into the saw blade. Further, the carriage jig shown in Cowley is not adapted to hold particularly long stock, as would be necessary to cut e.g. tongue and groove configurations in the edge of stock owing to its single clamp and need to fit in the miter gauge slot.
U.S. Pat. No. 4,732,182 issued Mar. 22, 1988, to Gorsha, clamps a work piece or stock with a single clamp to cut a dado or slot in the end of a rail. Gorsha is also adapted with an angled member to hold the work piece at a pre-selected angle. Gorsha, however, is slidably carried on the rip fence having a channel fitting over that element. Accordingly, this configuration shares substantially the same limitations as the previously mentioned carriage jig in that it provides no limitation on chatter, rotational movement components, and is only held down by the weight of the apparatus and the downward pressure of the operator who is also sliding the apparatus longitudinally.
Livick, U.S. Pat. No. 4,026,173 issued May 31, 1977, shows a saddle member slidably carried on a fence and guide rail and is substantially entirely addressed to ripping or sawing along the length of the stock. Livick uses two pointed levers to engage the stock for sliding longitudinal movement. Again, there is no disclosure of any mechanism to limit vertical movement or rotational movement or otherwise control e.g. chatter.
Other table saw accessories such as that shown in Atkins, U.S. Pat. No. 4,603,612 issued Aug. 5, 1986, are designed to accomplish other purposes such as limiting kick-back, particularly of small pieces as they may be moved past the saw blade, but in a position where their size makes it dangerous for insertion of the operator's hand to control the stock. The instant invention also provides a remedy to this phenomenon in connection with certain cuts or sizes of stock.